Bushings are widely used in chemical industry. The bushings are provided around chemical supply pipes between every two connecting ones for preventing leakage of the chemical products. The bushing is generally a ring having a metal strip of several loops with a strip shaped filler, such as asbestos, overlapped therebetween.
A conventional bushing forming machine is shown in FIG. 7. The bushing forming machine is intended for machining coiled stock, i.e., a metal strip M which is wound to form a spool S. The metal strip M is sent to a mold D through a pair of forming rollers R of a forming mill F. An opening O is formed in the mold D. A pneumatically operated roller P is engagable with the mold D. A free end of the metal strip M is inserted into the opening O of the mold D so that the metal strip M can be wound on the mold D by means of a foot pedal (not shown). Pressing the foot pedal one time, makes the mold D rotate one revolution. After the metal strip M is wound on the mold D for one revolution, a welder W makes a spot weld on the metal strip M for forming a rigid ring. Then, a filler (not shown) is fed into the metal strip M when the mold D continues rotating. The thickness of the bushing can be determined by the number of the rotations of the metal strip M. The filler is cut before the metal strip M rotates one more round. The welder W makes another spot weld on the metal strip M so as to form a ring-shaped bushing. The bushing is knocked down from the mold D by a plastic hammer so that a bushing is completed.
This type of forming machine requires a lot of man power, e.g., to insert the metal strip M into the opening O, to weld, to fill the filler, to cut and to knock down the bushing, etc. Therefore, a skillful operator is strongly required. The quality of the bushing can not be maintained at a certain level. The unit cost of the bushing is increased. In addition, the manually welding process is dangerous.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional bushing forming machine.